The 2021 amended return can ususally be efiled ... in the FILE tab you can choose to do so if allowed. If not allowed choose to mail it in and the mailing instructions should be in the PDF file of the return to mail. If not choose the PDF with the worksheets in the PRINT CENTER under the TOOLS tab.
If you still don't see them then use the PRINT to file option for the forms needed, SIGN the form, ATTACH all W-2 forms and anything with withholding on it and mail to the correct address depending on where you live : https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
